Hemoglobin (Hb) is the protein present in red blood cells which is responsible for the transportation of oxygen. Hemoglobin occurs in several variants, the most common form being hemoglobin A which comprises about 90% of the total hemoglobin found in blood.
A1c is a specific subtype of hemoglobin A. HbA1c is a glycated form of hemoglobin which is formed by the non-enzymatic glycation of the N-terminal valine group of the hemoglobin (Ao) beta chain. In a non-diabetic individual, around 90% of their total hemoglobin is present in a non-glycated form (hemoglobin Ao).
Proteins in solution in body fluids are continually subject to glycation processes. Glucose binds slowly to hemoglobin A to form the A1c glycated subtype. The formation of HbA1c reaches a steady state with about 3.0% to 6.5% of hemoglobin being of the A1c subtype. Most diabetic individuals have a higher blood glucose level than non-diabetics. This results in a higher HbA1c level in diabetic patients, with type 1 (juvenile) and type 2 (adult onset) diabetes sufferers having a HbA1c level ranging from about 6% to 15%.
Diabetes mellitus is a disease associated with poor glycemic control. Diabetes related complications may be reduced by long term monitoring and tight control of blood glucose levels. In the diabetic patient where blood glucose levels are obviously elevated, the HbA1c level can also increase.
The quantification of an individual's HbA1c level can act as an indicator of the average recent blood glucose level, which can in turn indicate the possible level of glycation damage to tissues, and thus the likelihood of possible associated diabetic complications if this state remains for the long term.
The HbA1c test is well established as a good index for an individual's glycemic control. The HbA1c test (which is also known as the hemoglobin A1c test, the glycated hemoglobin A1c test, the glycohemoglobin A1c test or the A1c test) is a laboratory based assay which reveals the average blood glucose level over a period of two to three months. The test measures the number of glucose molecules attached to hemoglobin. As erythrocytes are recycled after their normal lifetime of around 90 to 120 days, the measurement of the attached glucose in a current blood sample allows average blood sugar levels over the previous 2 to 3 months to be determined.
The use of the HbA1c test to monitor longer term glucose levels serves to complement the continuous day to day monitoring of blood glucose levels which can be performed directly by an individual determining their glucose concentration in blood, plasma or urine.
The monitoring of HbA1c levels is currently one of the best ways to monitor diabetes mellitus in order to assess whether the condition is being properly controlled (see, e.g., DCCT clinical study conducted from 1983 to 1993 by the National Institute of Diabetes and Digestive and Kidney Diseases). Specifically, the test allows a physician to ensure that diabetic patients are achieving optimal glycemic control and further ensures that diabetic patients are properly controlling their glucose levels between physician check ups.
It is recommended that all individuals with type 2 diabetes should have an HbA1c test at least twice a year. In cases where the resulting blood glucose level is too high, a repeat test at more frequent intervals is recommended. This testing results in around 40 million tests being conducted each year in Europe and the US alone.
Regular assessment of HbA1c levels allows an individual to manage their condition, this resulting in the delay or prevention of serious eye, kidney and nerve disease in people with diabetes. There is also an associated improvement in the general health of the individual.
Current methods used to measure HbA1c levels include column chromatography on ion exchange or affinity resins and high performance liquid chromatography (HPLC). However, none of these methods are ideal as methods for measuring HbA1c levels as they suffer from a number of drawbacks, such as not being accurate or easily standardized, being expensive and/or involving complicated procedures.
There accordingly exists a need for a fast, reliable and easy to use method for the accurate detection of HbA1c levels.